Spark plug



Nov. 9 1926.

G. FINCH SPARK PLUG Filed April 1. 1925 nch.

MMMZ 1 Patented Nov. 9, 1926.

UhllThU STATES ater GEORGE FINCI-I, OF LONG BEACH, CALIFORNIA, ASSIGNOR,BY DIRECT AND MESNE A EiE-GNIVIENTS, OF TWO AND ONE-HALF PER CENT TOAXEL W. MEIER, FZFTEEN PER GENT TO VERLIN K. AGAL, TVJO PER- CENT IOCLINTON MGGREGOB, ONE AND ONE- IIALF PER CENT TO WILLIAM M. SISGO ANDMARION SISGO, AND FOUR PER CENT TO T. M. GULLIOK, ALL LONG BEACH,CALIFORNIA.

seam: PLUG.

Application filed April 1,1 1925. Serial No. 19,822.

This invention relates to improvements in spark plugs.

The primary object of the invention is to provide an improved spark plughaving a hollow central electrode and a check valve therein, whereby airmay be. admitted through the hollow electrode to the interior of acylinder of an internal combustion engine. The admission of air inthismanner not only serves to re'duce'the partial vacuum formed in thecylinder during the suction stroke, but also provides for a morecomplete combustion therein, and will especially cause a completecombustion about the electrodes of the spark plug so as to keep them dryand clean.

it further object of the invention is to provide a spark plug having acore formed of insulating material in which is disposed a centralelectrode, and to provide an attaching means for fastening an electricalconductor to the spark plug, which attaching means is disposed in spacedrelation to the central electrode so that a spark gap will be formedupon the spark plug between the points of its electrodes and alsobetween the fastening means for the electrical conductor and the centralelectrode.

lVith the foregoing and other objects in view which will be mademanifest in the following detailed description and specifically pointedout in the appended claims, reference is had tothe accompanying drawingsfor an illustrative embodiment of the ing means which is'adapted to beassociated invention, wherein Figure 1 is a side elevation of the improved spark plug; F 2 is a vertical section taken substantially on theline 2-2 of Fig. 1;

Fig. 3 is a perspective view illustrating the central hollow electrode;

Fig. is a perspective view of the cap or valve seat which is mountedupon the central electrode;

Flg. 5 1s a perspective new of the retalnwith the valve seat shown inFig. 4 for maintaining the ball adjacent its seat; and

Fig. 6 is a horizontal section taken substantially on the line 6-6 ofFig. 2.

Referring to the accompanying drawings wherein similar referencecharacters destoward the central electrode.

ignate similar parts throughout, the improved spark plug consists ofa'body 10 provided with an annular flange 11, which body is threadedexteriorly below the flange, as indicated at 12. A shoulder 13 is formedupon the interior of the body, and the body is interiorly threaded, asat 14, above the shoulder. A core '15 having a bore 16 formed therein isprovided with a shoulder 17 adapted to engage the shoulder 13 uponthe'body 10. The core is maintained within the body 10 by means of agland or sleeve 18 which is adapted to be threaded or screwed into thebody about the core above the shoulder 17.

The body 10 is provided with an annular grounded. electrode 19, whichextends inwardly from the bottom edge of the body The central electrodeis hollow and is shown at 20 as consisting of a small section ofseamless tubing which has formed upon its lower end a tip 21 havinglateral apertures or passages 22 which communicate with the interior ofthe tubing. The tip 21 also provides a point 23 which is disposedadjacent the end of the grounded electrode 19. The tip 21 provides ashoulder upon the electrode and a sleeve of insulating material 24 isdisposed about the central electrode about the aperture 29 extends fromthe groove inwardly into the chamber 30 in which the ball 27 isdisposed. A. ring 31 formed of spring wire or the like has one end bentradially inward, as indicated at 82.- This ring is adapted to be placedabout the cap and occupy thegroove 28 with the end32 extending throughthe aperture 29 into the chamber below the ball 27 so as to maintain theball adjacent its seat, and thus prevent the ball from falling andclosing the bore 33 which is formed in the central electrode. The cap 25may have a flange 34 formed ill) adjacent its top which rests upon thetop of the core 15. It will be understood that by tightening the cap 25upon the electrode 20, the electrode will be rigidly held within thecore 15.

Upon the top of the core there is mounted a second cap having a stem 36extending upwardly therefrom and which is exteriorly threaded to receivea thumb nut 37. An aperture 38 is formed in the stem 36 and permits airto enter therethrough past through the aperture 26 and to be drawndownwardly through the bore 33 ant the lateral passages 22. It will benoted that the cap is disposed in spaced relation tothe cap so as toform a spark gap between the cap 35 and the central electrode. The thumbnut 37 serves as a fastening means for connecting an electricalconductor, such as a wire, to the spark plug.

The operation of the spark plug is as follows: Upon the downward orsuction stroke of the piston, a partial vacuum is formed in thecylinder. Air is drawn through the aperture 38 and escapes past thecheck valve provided by the ball 27 and flows downwardly through thecentral electrode. Upon the other strokes of the piston in whichpressure is developed within the cylinder, the ball check valve 27 isheld against its seat, so as to close the aperture 26. The tip 21 ispreferably formed of Monel metal, so that it cannot be easily burned. Byusing the mica sleeve 24:, the expansion of the central electrode istaken care of, as the mica is capable of being slightly compressed andin this manner the expansion of: the central electrode will not crackthe core 15 which is preferably formed of porcelain or the like. Byproviding the spark gap between the cap 25 and the cap 35, the electriccurrent is caused to jump between the caps and also between theelectrodes. The spark gap between the caps serves to control the currentwhen of high voltage. It the current is of too great voltage, the sparkgap tends to break it down.

On the other hand, if the current is of lowv voltage, it tends to buildup before jump ing the gap, and in this manner a very eflicient sparkplug is produced. The break ing of the vacuum in the cylinder of aninternal combustion engine reduces the pumping of the oil, and theadditional supply of oxygen derived from the admission of air aids incausing a complete combustion of the fuel within the cylinder. By theuse of the mica sleeve 24, if the porcelain core 15 should becomecracked, a short across the plug is prevented, which might otherwiseoccur by the creation of the spark between the central electrode 20 andthe body 10 or the gland 18.

It will be understood that various changes in the detail of constructionmay be made without departing from the spirit or'scope of the inventionas defined by the appended claims.

I claim:

1. A spark plug having a core formed of 1 second cap having an upwardlyextending stem in which a passage is formed which is also in alignmentwith the bore in said electrode, and means associated with said stem forsecuring an electrical conductor thereto.

2. A spark plug having a core formed of insulating material, a centralelectrode disposed within said core, said electrode having a boreextending longitudinally therethrough, a cap threaded onto the upper endof the electrodehaving an aperture therethrough in alignment with thebore in the electrode, a valve seat upon the under side of said cap, aball disposed within said cap adapted to seat upon said seat, means formaintaining said ball adjacent said seat, a second cap mounted upon saidcore in spaced relation to the cap on the electrode, said second caphaving an upwardly extending stem in which a passage is formed which isalso in alignment with the bore in said electrode, means associated withsaid stem for securing an electrical conductor thereto, the bottom ofthe electrode being provided with a tip having lateral passagestherethrough communicating with the bore in the electrode and providinga point for the electrode, and a mica sleeve disposed between theelectrode and the core.

In testimony whereof I have signed my name to this specification.

GEORGE FINCH.

